Storage buildings such as barns and the like commonly include horizontally sliding doors which are suspended by trolley hangars from a rail extending horizontally across the top of the associated doorway. In the so-called pole buildings there is no threshold which extends across the bottom of the doorway. Such a door is relatively large in cross-sectional area and unless it is held at the bottom it can be readily blown upwardly away from the building causing serious damage to the door system and oftentimes to the building itself.